This invention relates generally to the field of user interfaces for electronic devices such as computers and machine controllers. More specifically, the invention relates to touch sensitive user interfaces and methods for effecting movement control of, for example, a cursor on a computer screen or for directing object movement of a machine or robot.
User manipulated devices are commonly used today in conjunction with electronic devices to control the movement of a pointer or cursor on a graphics screen or to directly control object movement of an apparatus such as a machine or robot. Some of these devices may be characterised as isotonic devices which map the user manipulation of the devices directly onto the object, such as a cursor. Some examples of isotonic devices are computer mice, trackballs, touch-pads and digitizer tablets. Other of these devices may be characterised as being isometric, meaning they relate the direction and magnitude of the force or torque applied by the user to the devices to the cursor or object movement. An example of an isometric device is a joystick.
Two fundamental operations with an input device such as a computer mouse are xe2x80x9cpointingxe2x80x9d and xe2x80x9cdraggingxe2x80x9d. In pointing the user manipulates the mouse to cause the cursor to move onto a target. In dragging the user moves an object into a target area. Human-computer interaction study shows that in general, the mouse movement is characterised by a large primary movement followed by smaller submovements. These movements correspond to gross positioning and then fine positioning of the object by the user manipulation of the mouse to align the object or cursor with the target.
The sensitivity of movement control or gain is the ratio between the distance the isotonic device must be moved to cause a given movement of the object such as a cursor on the display. This is also known as the Control-Display ratio between the resolution of the display, in terms of pixels and the resolution of the isotonic input device in terms of dots per inch (dpi).
In general, a high gain device is rapid in initial gross positioning but difficult to control when needing to make small precise movements. A low gain device allows small precise movement of the object and therefore easy (and quicker) fine positioning but is inefficiently slow at gross positioning. For a fixed gain input device, the trade-off between initial gross positioning versus final fine adjustment typically results in a U-shape gain-performance curve with best performance at a moderate gain level.
The demand on control sensitivity varies with the application. For general applications in graphical user interface (GUI), such as Windows by Mircosoft, the cursor is generally used to select medium sized icons on a medium resolution display and this is generally suitable to work with a fixed gain input device. On the other hand, often in CAD or graphic work a user has to select one target from very many, closely spaced, even pixel width target areas, such as an intersection of two lines. Such fine positioning can be very difficult with a device which has too high a gain and can be very stressful to the user. It is therefore desirable to have a low or moderate gain device for the fine control. However, the resolution of the display for CAD or graphic work is usually higher such that moving the cursor across a high-resolution display with a lower or moderate gain input device requires too much hand movement and can be tedious.
Several attempts have been made in the past to provide a more user friendly device. U.S. Pat. 4,963,858 to Chien discloses a mouse using accelerated motion switches to select predetermined gain. Another approach is taught in U.S. Pat. No. 5,793,354 to Kaplan. A separate gain control button or foot pedal is used to change the gain using an electronic circuit in response to the amount of depression of the button or pedal. Another version is taught in Canada Patent 2,203,387 to Even in which a variable transmission element is inserted between the rotating ball of the conventional mouse and the digitizing encoder system and activated by a lever. However, the use of a separated control button, or pedal, or lever, requires the user to coordinate the use of different limbs at the same time which is awkward and can be difficult to master.
A typical isometric joystick responds to a force exerted by the user""s hand and is usually found embedded in the keyboard of a laptop or a notebook computer. The cursor moves in the tilting direction of the joystick and generally the cursor speed is determined by the force exerted. The same dilemma of gain to controllability applies to joysticks. Furthermore, it has been found that pointing times could be expected to be perhaps 20% slower than for a mouse performing the same tasks. Another concern is the xe2x80x9cfeelxe2x80x9d, or the lack of kinesthetic feedback because there is so little movement of the user""s limb at the point of force application. For example, to slow down the user has to release pressure on the joystick by just the right amount. Too little, and the cursor stops short of its goal. Too much and the cursor shoots past. Again, this requires good hand eye coordination which can be difficult to master, tiring to use for any extended period and frustrating in practice.
Various attempts have been made to improve the kinesthetic response of the isometric joystick. U.S. Pat. No. 5,805,137 to Yasutake describes a 3D input controller and suggests that the speed of the cursor or object movement in a given direction will be responsive to the magnitude of the force applied to the corresponding force-sensitive pads. However, no structures or methods are taught as to how to ergonomically achieve this. Instead the disclosure teaches that determination of movement and force are two separate operations on a touchpad. The cursor response suffers a time delay from the application of a force due to computational requirements. The time lag between action and object response is disorienting and unacceptable.
U.S. Pat. No. 5,815,139 to Yoshikawa et al. describes a touch activated input device that teaches that the applied force on a force-sensitive touch pad can be used to vary the speed of movement of the object. The complication of using instantaneous force as a variable (which is computed and has an attendant lag) is simplified by dividing the forces into several levels and using a lookup table for a speed factor. However, the device is basically a joystick button on top of a touch pad and does not have the intuitive kinesthetic feedback of an isotonic device, because the operations are separate and thus still disjointed.
What is desired is a simple to use ergonomic device which permits cursor or object movement to be accomplished in a single operation of steering the pointer, at an appropriate speed range, including smooth acceleration and deceleration, by means of a touch control input method. Therefore, in one aspect, the present input device is a touch control device manipulated by the touch of the user that permits control of a computer or a machine. A human limb can send and receive information through both the force/torque and displacement/rotation. What is desired is user touch control that responds ergonomically, that is, in a manner more like a human limb responds. What is desired is to overcome the limitations of a single input control mode such as provided by the movement with the isotonic device only or as provided by the force with the isometric device. What is desired is a method and an apparatus to smoothly blend the two control modes, isotonic and isometric, together to compliment each other to improve the ease of use of the touch activated input control. It is therefore desirable to have an improved touch control input method and device that provides a user interface with kinesthetic and tactile feedback, that allows the user to vary the gain easily and smoothly, and a mechanically simple apparatus that overcomes the disadvantages of the prior art methods and devices discussed above.
Therefore, according to one aspect of the invention there is provided a method of touch control of a user input device, said method comprising the steps of:
providing a contact surface of known configuration mounted in a support and having a force sensing means operatively connected to said contact surface for sensing user contact with said contact surface;
contacting said contact surface to cause said sensing means to generate output signals corresponding to said contact;
using said output signals to provide a relative measure of a tangential force applied to said contact surface by said user contact; and
using said relative measure of tangential force to control movement of an object in response to said user contact with said contact surface.
According to another aspect of the present invention there is provided an ergonomic touch control input device, said device comprising:
a manually manipulable member having a contact surface of known configuration;
a support in which said manipulable member is mounted; and
a force sensing means operatively connected to said manipulable member for sensing user contact with said contact surface, said sensing means sensing a contact force at said contact surface other than a normal force and generating output signals related to said contact force for use in controlling an object""s movement and for controlling the gain of such device to effect movement control, all in response to said user contact.